The two main components of off-roading are simple: overcome obstacles and maintain traction. In fact, aftermarket mods thrown onto off-road rigs are aimed at beefing up a vehicle’s ability to perform these two tasks. A locking differential is certainly of no exception. But the debate rages on among off-road enthusiasts as to which is better: Air Lockers or E-lockers?

Awhile back, we broke down the science behind open, limited slip, and locking differentials in a Tech Corner right here on the Engine Block. So, if you don’t yet know the basics, click here for a quick lesson.

For the rest of ya’s, here’s the diet version:

A differential is designed to allow both wheels to rotate at different rates of speed, essentially allowing a vehicle to turn properly. Most stock vehicles come with open differentials, and in some cases limited slip differentials. While both of those setups are fine for pavement driving, they are less than ideal for off-road excursions. In low traction situations, you don’t want to be caught with one tire spinning faster than the others—if they’re even turning at all. A locked differential, which locks the axles together so that both wheels receive full power from the engine at all times, will provide the maximum traction you need to conquer obstacles on the trail.

Understand Your Options

Before we get into which is better— air lockers or e-lockers —it’s important to understand the purpose of (and differences between) each.

For street use, locked differentials pose a problem. Namely, with those axles locked together, turning is reduced and places strain on your equipment. So, unless you have an off-road vehicle expressly dedicated to trail-riding, a permanently locked differential is going to cause more headaches than fun. Enter air lockers and e-lockers. These units are designed to allow users to switch from an open differential to a locked differential as needed, either through air pressure or an electronic switch.

Air Lockers

Since ARB is the go-to brand for this style of locking differential (also popular is the Yukon Zip Locker), let’s use one of its units as an example. Inside of an ARB air locker, you’ll find all the familiar components that are housed in an open diff. However, when pneumatic pressure is applied, a locking collar slides forward, effectively locking the gears together. This action converts the open differential into a spool.

A source of on-board, compressed air is necessary to provide the air pressure, and is usually linked up to a switch on the dash. When the switch engages, the air pressure is supplied through the air lines to the differential. Until the pressure is let off, the collar inside will keep those gears locked together.

A hard selling point for air lockers is that, because they work on pneumatic pressure, there is a near-immediate engagement of the system. In fact, the ARB air locker mentioned above, engages in less than a second, and it can be switched on at any vehicle speed. (That is, “as long as the axle shafts are spinning at equal speeds with no differential of speed between the wheels of that axle,” says the manufacturer.)

This is a major feather in the cap for air lockers—as those few seconds and inches of rotation can make a big difference when navigating tricky trails.

E-Lockers

E-lockers, on the other hand, use an electromagnet to convert the differential into a spool. Inside an e-locker, you’ll find that the magnet pulls two roller cams apart. After this happens, ball bearings are used to keep them separated. The separation of these cams pushes heavy pins down into the side gear of the differential, locking them together. These systems also work with the use of a switch that is mounted inside of the vehicle.

E-lockers do not rely on an outside source of power, other than 12-volt power. While this is an advantage over air lockers (which need both the 12-volt and the compressor), e-lockers rely on roller cams for engagement. This means that even after the switch is flipped, a degree of rotation will need to occur in order for the locking mechanisms to engage. Improper operation of the system will result in damage to interior moving parts, so a level of care needs to be taken when these lockers are put to use.

Often, e-lockers are used as factory equipment on many vehicles. (Toyota, Ford, GM, and Chrysler all sell models that come stock with this style of locking differential.) In the debate of air lockers or e-lockers, this tends to add fuel to fire. It gives the sense that because manufacturers rely on e-lockers, so should the aftermarket. However, when these factory units fail, that gives the air locker camp more ammunition.

So, which is it? Air lockers or E-lockers?!

Well, it’s not that simple…

The Investment

Remember how we said air lockers have the added advantage of almost immediate engagement? Well, that convenience comes at a cost. As we stated in our previous Tech Corner, factoring in the additional expense of either an on-board air compressor or CO2 tank, not to mention the parts and labor to install, the upgrade can run you near $1,500 just to update one carrier.

And while e-lockers may be more cost-effective, there are still labor costs to consider as well. Unless you have a reasonable amount of experience working on any differential, you really want to take this job to a professional. Ideally, you want a shop that has experience working specifically with locking differentials for off-road vehicles.

Dan Guyer, Wheel and Tire Category Manager at Keystone Automotive, is our go-to guy for all-things-off-road because of his extensive knowledge and real-world experience. When it comes to what’s easier to install—air lockers or e-lockers—he offered this advice: “The electronic stuff—there’s a wire in there that can fail. And on the air stuff? Well, there’s a line in there that can fail. If you go to an installer who’s really good at it, then it really doesn’t matter. The installer knows how to route things and use quality materials. You go to a well known off-road shop and they’re going to do it right.”

Front or Rear

When weighing the pros and cons (as well as the cost) of air lockers or e-lockers, consider whether or not both differentials need to be locked. How hard are you looking to push that rig? Obviously, by installing lockers to both the front and rear of the vehicle, you will reach ultimate potential in terms of traction. However, unless you’re pushing it to extreme levels, you really don’t have to go this route.

If you’ve settled on only upgrading one, deciding between front or rear should be balanced with intended purpose. Do you mostly use that truck for hauling and towing, with occasional off-road wheeling thrown in for fun? A rear-locking differential may be the best bet for you, as the weight will be primarily transferred to the rear wheels, helping to maintain traction and towing/payload capacity.

If hardcore off-roading is more your game, consider the front-locking differential. Research indicates giving that additional bite to the front of the rig makes it easier to pull through difficult situations, rather than trying to push.

Additional Costs

As with most aftermarket modifications, the buck doesn’t exactly stop there. While the differential is being pulled apart, you’ll want to consider installing a new ring and pinion as well. The carrier is responsible for telling the wheels when to spin, not how much. If you’re looking for maximum off-road traction, a lower ring gear goes a long way.

Even if you have a decent gear ratio installed, mileage and hard use could have worn it down. Throwing old stuff on new parts is begging for additional costs to be made sooner down the road, so you might as well address it now. And of course, reinforcing the setup further with stronger axles is always a wise investment.

Pound for Pound: Deciding Which One YOU Need

It’s always important to get the best bang for your buck. As we mentioned before, some people feel that since automakers opt for e-lockers on stock vehicles, they must be better. Guyer weighed in on the discussion with some great insight: “When you buy quality components, it doesn’t matter the way that they lock. It’s about the level of quality and what kind of warranty you got with it… Typically, [aftermarket parts] will be made with better materials than the OE stuff because they’re not made for ‘Hey I just bought a brand-new F-150!’ They’re made for ‘Hey I’m taking my Jeep out to Rausch Creek, or Johnson Valley, or Moab—and I’m going to beat on it. I need it to survive.’ That’s the aftermarket. They take what the OE gave you and they improve upon it. That’s the beauty of it.”

So, if e-lockers are for you, then it’s still wise to turn to the aftermarket.

In reality, either option is fine for light-duty use. Both will effectively lock up the wheels on command, increasing traction and fun on the trail. But for those hardcore applications where a split second and just a few scant inches of rotation make all the difference—well, we have to pick a side. Air lockers are the real winner. Yes, the cost is higher, but the reliability and instant engagement dubs them the superior unit.